Three-passage valves generally comprise a body with three passages, a valve mechanism and a single control lever which makes it possible to avoid erroneous operation.
However, these valves have disadvantages. When closing a first passage and opening a second, the control lever successively passes from a first position in which the first passage is open, to a middle position in which both passages are closed, and on to a second position in which the second passage is open. Now, during these operations, the various parts of the valve mechanism pass successively in front of each of the passages so that the same zones of the valve mechanism are successively in relation with each of the passages. Therefore, the quality of the sealing between each passage and the others is related to the quality of the sealing of the other passages.
Preferred embodiments of the present invention provide a three-passage valve in which the quality of sealing of any one passage is independent from that of the others.